Ground control to Major Tom.
Commencing countdown,
engines on.

 

("Space Oddity," by David Bowie, 1969)

 

COMPARING OLD AND NEW CONTROL ROOMS

The pictures at the top of this PTOA segment show Control Board Operators at work in modern, digitized control rooms.

A modern, digitized control room with computers and computer screens has a Distributed Control System (DCS) of some type.

The word "distributed" is an accurate description; the hardware/software cabinets that relay data between the processing area and the control room are not necessarily located in the control room but rather distributed throughout the plant area.

A non-digitized control room is in the below picture. Each individual controller, indicator, recorder or alarm is mounted on panels that stretch across the length of the room.

 

No kidding! Behind each one of those indicators, controllers, recorders, and alarms are dedicated wires and components that relay information between the control room and the processing area.

Remember that TI that the outside Process Operator was recording in the first two PTOA segments?

If that TI reading was to be "brought into the board" for the Control Board Operator to view, wires and components from the processing area to the control board would be required just to monitor that one process temperature.

 

HOW ARE THE DIGITIZED AND NON-DIGITIZED
CONTROL ROOMS ALIKE?

Both of the control rooms are currently in use.

Both control rooms use automated technology to centralize oversight of process status indicators, recorders, controllers and alarms.

Functionally, both Control Rooms are identical.

The below four enumerated actions are a simplified description of how a Control Board Operator interacts with a controller that is mounted on a control room panel or on a screen in a DCS system. Later PTOA segments are dedicated to understanding control loop theory.

1. Both control rooms ultimately receive transmitted signals of some type from the processing area. These signals relay information about the current status of the process variables (Temperature, Pressure, Flowrate, and Level).

2. The incoming signals from the field are converted into information and data that a human being can understand. That human being is a Control Board Operator.

Only when necessary, the Control Board Operator makes changes on the controllers to keep the process variables where they need to be to make desired products. Smaller changes that take more time to complete are made in automatic mode; big, fast changes are made in manual mode.

3.The adjustments that the Control Board Operator makes to the controllers leave the control room as an altered output signal; the signal is either greater or less than it had been.

These out-going signals are eventually received by an automated valve that is located back out in the processing area.

4. The change in output signal informs the automatic valve that a change in its position is needed; the automated valve will either open a bit more or close a bit more to maintain Temperatures, Pressures, Flowrates, and Levels where they need to be to make the desired products.

 

Take Home Messages:  Both Distributed Control Systems (DCS) and non-digitized control rooms exist in processing facilities and PTOA Readers and Students might eventually work in either environment.

Both DCS and non-digitized control rooms centralize indicating, controlling, recording and alarming functions of automated process control.

Functionally, DCS and non-digitized control rooms are identical. The Control Board Operator/Controller interactions with input from and output to field instruments are identical in both environments. 

©2015 PTOA Segment 00012
Process Industry Automation

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